Body Systems

1. the main control center of the body that directs all actions
3. a blood vessel that brings blood back to the heart
5. a large dome-shaped muscle under the lungs that controls breathing
7. an invader such as a virus, bacteria, or fungus that can make the body sick
9. a small, thin tissue that connects muscles to bones
10. the hard substance that gives shape and protection to the body and stores minerals
13. a tiny air sac in the lung where oxygen and carbon dioxide are exchanged
14. a tissue that moves bones by tightening and relaxing
16. the basic cell of the nervous system that carries messages through the body
18. an organ that processes nutrients, stores sugar, and breaks down harmful chemicals
19. a bundle of axons and dendrites that sends signals between the brain and the body
20. the main airway, also called the windpipe, that carries air to the lungs
21. a large blood vessel that carries blood rich in oxygen away from the heart
22. a large muscular chamber where digestive juices break down food

2. a long tube where nutrients from food pass into the blood
4. an immune cell in the blood that fights disease and infection
6. the place where two bones meet
8. the main organ of the respiratory system that takes in oxygen and releases carbon dioxide
11. a special protein that breaks down food into smaller molecules the body can absorb
12. the smallest blood vessel, where food and oxygen pass into body cells
15. a long bundle of nerve fibers that connects the brain to the rest of the body
17. the muscle that pumps blood through the whole body